Process and dual-detector apparatus for analyzing gases



M. E. KROGH Oct. 21, 1958 PROCESS AND DUAL-DETECTOR APPARATUS FOR ANALYZING GASES Filed Jan. 28. 1953 amm I INVENTOR. Milton E. Krogh, deceased by Mary Frunqes Krogh,

ATTEST Execuirik Attorney United States Patent PROCE SS AND DUAL-DETECTORtAP-PARATUS FOR ANALYZING GASES Milton E. Krogh, deceasedflateofDallas, Tex., by Mary Frances Krogh, executrix, Dallas,'Tex., assignor to The Atlantic Refining Company,-TPhiladelphia, Pa., a cor- "porationof-Peunsylvania Application January 28, 1953, Serial No. 333,694-

*Claim's. (Cl. 123-232) This invention .relates to apparatus for detecting the presence of combustible gases in a stream of gases oi unknown composition, and more particularly to apparatus for determining whether combustible Igase's separated from {the returning mud stream during the drilling of a well comprise predominantly methane .to the substantial exclusionofhigher hydrocarbon gases, or comprise higher hydrocarbon gases with or Without the presence ofmethane.

In the .drillin'gof oil wells .by the rotary drilling method wherein-a ,drillingfluid, or mud, is used :to lubricate the bit .andlcarrry cuttings out of the well, it .has recently become fairlycommon practice-to examine the returning .mudstrcam .for the presence therein of hydrocarbons, whereby .to determine whether the drill bit has pens trateda hydrocarhonsbearing .foi'mation. According to the .one well known ..method, a..gas trap is connected to the returning mud line to continuously separate and withdraw aportion of the gases which may .be present in/the returning mud stream. .Gases thus withdrawn .ftom the mud stream .are :mixed with air and .thenlpasse'd .to .a combustible-gas detector which produces electrical signals in accordance with the concentration of gaseous (hydrocarbons present lin=such gases. Usually, and preferably, the gas detectoris connected with a recording apparatus on which the electrical signalsfrom the gas derector are recorded citherin accordance with welldepth oras a function of-time.

' prise the highernormally gaseouslhydrocarbons the penetrated forinationis probably an oil-hearing formation.

Thereuare, of course, presently available combustiblega-s'detectors capable of adjustment for detecting either the presence of the highergaseoushydrocarbons irrespective of the presenceof methane, or thepresenceof all normally gaseous hydrocarbons including methane. However, there has not heretofore been provided any completely integrated and automatically operated apparatus which is capable of taking a .sample of gas from the returning vmud stream from a drilling well and automatically giving an indication as to :whether said gas sample contains predominantly methane or whether it also contains substantial componentsof the higher hydrocarbons. v

Accordingly, itis .oneobject-oftthe present invention to provide an apparatus fordetectingigaseoushydrocarbons in the returning mud stream from an oil well and auto- 2,857,251 Patented Oct. 21, 1.9.5.8

than methane, or predominantlymethane to the substantial exclusion of higher hydrocarbons.

It is another object of this invention to provide a combustible-gas detecting and recording apparatus having two detector elements, one of which is adaptable to indicate the presence of all normally gaseous hydrocarbons including methane, and the other of which is adapted to indicate the presence of only higher gaseous hydrocarbons irrespective of the presence of methane.

It is a further object of this invention to provide apparatus for examining the gases separated from the returning mud-stream from a drilling well comprising a first detector for detecting'the presence of'higher, gaseous hydrocarbons irrespective of the-presenceof methane, a second detector capable of detecting the presence of all normally gaseous hydrocarbons including methane, a recorder adaptable to receive and record signals from either of said detectors, and automatic switch means for periodically and alternately connecting each of said detectors to said recorder.

Other objects and advantages will become apparent from the following detaileddescription taken in connection with the appended drawing,

In the drawing Figure .1 is a schematic c'iiagramof a preferred embodiment of the apparatus of the present invention.

'Figure'2 is a schematic representation of the electrical circuit of atypical filament-type combustible-gas detector Which forms a component part of'the apparatus of this invention.

Figure 13 is a representation of a section of a recording chart which might be produced by .the apparatus of Figure 1.

Briefly, the apparatus of the present invention comprises two combustible-gas detectors through which .a

sample of gas of unknown composition is adapted .to pass, a recorder for recording signals emitted by each of the detectors in accordance with the concentration. of combustible gases detected, and automatic switch means for-alternatively and periodically connecting each of the detectors to the recorder.

In the drawing numeral Idenotes the flow line through which drilling fluid returns from the drill hole to the mud pit. Attached at .any convenient location 2 along line 1, as-by welding, is gas trap 3 which-is in communication with the interior of line 1, .andin which gas liberated from the drilling fluid will collect in the well 7 known manner. Gas trap 3 may be of any conventional design or type. The gas collected in gas trap 3 is mixed with air which enters gas trap 3 throughnipple 4, and is then carried'by conduit '5 through a first combustiblegas detector 6, which by way of illustration is preferably a detector of the well known hot-filament type which produces an electrical signal proportional to the amount of, gaseous hydrocarbons higher than methane which are present in the gas stream; and thence through a second combustible-gas detector 7 which is also preferably of .the hot-filament type but which produces an electrical signal proportional to the amount of total gaseous hydrocarbons, including methane, present in the gas stream. After passage through the gas detectors, the gas is exhausted to the atmosphere through vacuum pump 8. The electrical output signal from detector 6 is supplied through wires 9 to one set of fixed terminals 10 of switch 11, and the electrical output signal of detector 7 is supplied through wires 12 to another set of fixed terminals 13 of switch 11. A set of movable terminals .14, to whichare connected wires '15, are adapted to be moved selectively .to contact with fixed contacts 10 and 13 whereby to selectively supply the electrical signals from wires 9 and 12,

are not within the scope of the present invention since detectors of this type, such, for instance, as illustrated in the patent to Bliss et al. No. 2,514,690, are well known to those skilled in the art. Such detectors, as illustrated in Figure 2, comprise a filament 19 which forms one arm of a Wheatstone bridge circuit 20 and which is adapted to be contacted by the gas to be analyzed. The other arms of the bridge comprise a compensator element 21, and resistances 22 and 23, respectively. Voltage supplied by battery 24, or other suitable source, across points 25 and 26 of bridge 20 serves to maintain filament 19 at an elevated temperature suflicient to cause ignition of the desired combustible components of the gases which pass in contact therewith. Output leads 27 and 28, which, it will be understood, correspond to leads 9 of detector 6 or leads 12 of detector 7, are connected across point 29 and potentiometer 30 to supply the output of the bridge circuit to a suitable measuring and recording device. It will be understood that potentiometer 30 is so adjusted that there will be no voltage difference between leads 27 and 28 when gases to which-filament 19 is exposed contain no combustible components ignitable at the temperature of the filament. It will be appreciated by those familiar with such detectors that the rise in temperature of filament 19, due to the ignition of combustible components which later appear in the gases contacting the filament, acts to change the resistance of the filament and thus causes an unbalance of bridge 20 and a measurable difference in potential between the output leads 27 and 28.

As is well known to those skilled in the art, methane, being more stable than the higher normally gaseous hydrocarbons requires a higher temperature to induce ignition. Therefore, it will be appreciated that the filament of a typical hot-filament detector may be operated at a temperature which is sufliciently high to induce ignition of the higher hydrocarbons which come in contact therewith and yet be insensitive to the presence of methane.

On the other hand, if the filament of the detector is operated at a temperature suflicient to induce ignition of methane which passes in contact therewith, it will also induce the ignition of higher gaseous hydrocarbons which also contact it. Thus, by passing a sample of gas first through a detector having the filament at a temperature only suflicient to cause ignition of the higher hydrocarbons which contact the filament, and then through a detector having its filament at a temperature sufficiently high to cause ignition of methane and the higher hydrocarbons which come in contact therewith, and comparing the electrical outputs of the two detectors, it is possible to determine whether the sample of gas contains predominantly methane, or methane accompanied by substantial amounts of the higher hydrocarbons, and the proportions of these gases.

Those skilled in the art will appreciate that the operating temperature of the filament of the detector which is adapted to detect only the higher hydrocarbons may be established empirically by adjusting the temperature in the presence of gas of known composition to a temperature such that it will cause ignition of the higher hydrocarbons, but will not cause the ignition of methane alone. Likewise, the temperature of the filament of the detector for detecting all hydrocarbons, including methane, may be established empirically by adjusting the temperature thereof sufliciently high to induce the ignition of methane in a sample of known composition, Satisfactory results 4 have been obtained by employing operating temperatures of approximately 450 C. and approximately 550 C., respectively, for the filaments of the two detectors.

In connection with the specific apparatus described herein, therefore, it will be appreciated that the filament of detector 6 is adjusted to a temperature sufficient to cause ignition of normally gaseous hydrocarbons higher than methane which pass in contact with the filament, but not methane; whereas the filament of detector 7 is adjusted to a temperature sufficient to induce ignition of all normally gaseous hydrocarbons, including methane, which pass in contact therewith.

Referring now to switch 11, it is to be understood that this switch may be of any suitable type for alternatively connecting either wires 9 or wires 12 with wires 15, which are in turn connected to recorder 16. By way of illustration, switch 11 has been shown in Figure 1 as comprising fixed terminals 10 to which wires 9 are connected, fixed terminals 13 to which wires 12 are connected, and movable terminals 14 which are secured to movable member 31. In the particular embodiment shown, movable member 31 is adapted to be operated by rod 32 which forms the armature of solenoid 33, the coil of which is adapted to be supplied with current periodically from timer controlled source 34 through leads 35. Movable member 31 is adapted to be held in its extreme right-hand position by spring 36, and to be moved to its extreme left-hand position upon energization of the coil of solenoid 33 which serves to move rod 32 to the left, as will be appreciated by those familiar with the operation of solenoids. The current supplied to leads 35 may be obtained from any source, not shown, such as a 115-volt -cycle supply line, or from batteries; and the timing mechanism of timer controlled source 34 may be either mechanical or electrical, these details not being a part of this invention.

In operation, with mud flowing through line 1, the gas and air mixture entering gas trap 3 will be drawn through conduit 5 and through detectors 6 and 7 under suction provided by suction pump 8. Timer-controlled source 34, by alternately supplying and discontinuing power to solenoid 33, causes the movable member 31 of switch 11 to reciprocate between its right-hand and lefthand positions whereby to alternately connect movable terminals 14 with fixed terminals 13 and fixed terminals 10. Timing mechanism 34 may be adjusted to cause movable member 31 to operate on any desired cycle; however, an arrangement whereby movable member 31 reverses its position every 30 seconds has been found to be satisfactory.

With such an arrangement it will be appreciated that during one 30-second interval, the stylus 17 of recorder 16 will occupy on chart 18 a position indicative of the concentration of total gaseous hydrocarbons, as indicated by the signal from detector 7, transmitted through wires 12, switch 11, and wires 15, and that during the next 30- second interval, the stylus 17 will occupy a position on chart 18 indicative of the concentration of gaseous hydrocarbons higher than methane, as indicated by the signal from detector 6, transmitted through wires 9, switch 11, and wires 15. Thus if stylus 17 indicates a positive reading when recorder 16 is connected with detector 7, and a zero reading when recorder 16 is connected with detector 6, this fact is indicative of the presence of methane, without higher gaseous hydrocarbons, in the gases flowing through conduit 5 and the detectors. 0n the other hand, it will be understood that when stylus 17 indicates a positive reading both when recorder 16 is connected with detector 6 and when it is connected with detector 7, that fact indicates that gaseous hydrocarbons higher than methane are present. Also, it will be appreciated that since detector 7 indicates concentration of total gaseous hydrocarbons and detector 6 indicates only concentration of gaseous hydrocarbons higher than methane, a comparison of the respective positions of stylus 17 when the an infinitesimally small proportion of the total gas flowing in the stream actually .directly contacts the filament, it will be appreciated that the composition of the total gas mass comprising 'thestream is not substantially affected by the ignition caused-by the-filament. Thus, in the specific apparatus disclosed-in Figure 1, the signalgenerated by detector 7 will, for all practical purposes, be proportional to the amount of all normally gaseous hydrocarbons originallypresent in the stream of gases as it left gas trap 3, even though there may bepresent therein higher gaseous hydrocarbons ignrtaole at-tne temperature or the .filament ot detector 6.

in Figure 3 there isshown a' section of a chart of the type which might be produced by 'the recorder of an apparatus of the type described above. On this chart 18 the segments 37 represent the position of the stylus 17 when recorder 16 was connected "with the output of detector 7 (that is, the detector having its filament at a temperature suflicient to ignite methane) and segments 38 represent the position of the stylus when recorder 16 was connected to the output of detector 6 (that is, the recorder having its filament at a temperature suificient to ignite only hydrocarbons higher than methane). From an examination of the section of chart shown in Figure 3, it will be seen that the combustible gases, detected as indicated between points 39 and 40 on the chart comprised predominantly methane, whereas the gases indicated between points 41 and 42 contained substantial amounts of higher hydrocarbons as well.

While there is shown and described only one embodiment of this invention, it will be appreciated by those skilled in the art that many changes might be made there to without departing from the scope of this invention; for instance, the relative positions of detectors 6 and 7 may be reversed, so that the gas flowing through conduit 5 first comes in contact with the detector capable of de tecting all gaseous hydrocarbons, including methane, and thereafter comes in contact with the detector which is capable of detecting only the higher gaseous hydrocarbons. Therefore, it is to be understood that this invention is not to be limited by the above description but is to be limited only in accordance with the appended claims.

What is claimed is:

1. An apparatus for detecting and recording the presence of hydrocarbons in a stream of gas of unknown composition and for distinguishing between methane and normally gaseous hydrocarbons higher than methane, the combination of a first filament-type combustible-gas detector having a filament, means for maintaining said filament of said first detector at a temperature suificiently high to cause ignition of normally gaseous hydrocarbons including methane, whereby said detector will generate a signal proportional to the amount of such gaseous hydrocarbons in said stream, a second filament-type combustible-gas detector having a filament and being of the same character as said first detector, means for maintaining said filament of said second detector at a temperature only sufiiciently high to cause'ignition of higher normally gaseous hydrocarbons to the exclusion of methane, whereby said second detector will generate a signal proportional to the amount of higher normally gaseous hydrocarbons in said stream, means for continuously passing said stream of gas in contact with the filament of said first detector and then the filament of said second detector, recording means having one stylus for recording the signals from either of said detectors, and automatic switch means for selectively and alternately connecting said detectors to said recording means.

2. An apparatus for detecting and recording the presence of hydrocarbons in'a stream of gas of unknown composition and for distinguishing "between methane and nor mally gaseous hydrocarbons higher than methane, the combination of a first filament-type combustible-gas detector having a filament, means for maintaining said filament of said first detector at a temperature sufficiently 'high to cause ignition of normally gaseous hydrocarbons said filament of said second'detector at a temperature only sufliciently high to cause ignition of normally gaseous hydrocarbons to the exclusion of methane, whereby said second detector will' generate-a signal'proportional'to the amount of higher normally gaseous hydrocarbons in said stream, meansfor continuously passing said stream of gas in contact with thefilament of said first detector and then .the filament of said second detector, recording means having one stylus for recording the signals from either of said detectors, switch means operable to selectively and alternately connect either of said detectors to said recording means, and automatic timer controlled operating means for periodically operating said switch means.

3. An apparatus for detecting and recording the presence of hydrocarbons in a stream of gas of unknown composition and for distinguishing between methane and normally gaseous hydrocarbons higher than methane, the combination of a first filament-type combustible-gas detector having a filament, means for maintaining said filament of said first detector at a temperature sufiiciently high to cause ignition of normally gaseous hydrocarbons including methane, whereby said detector will generate a signal proportional to the amount of such gaseous hydrocarbons in said stream, a second filament-type combustible-gas detector having a filament and being of the same character as said first detector, means for maintaining said filament of said second detector at a temperature only sufiiciently high to cause ignition of higher normally gaseous hydrocarbons to the exclusion of methane, whereby said second detector will generate a signal proportional to the amount of higher normally gaseous hydrocarbons in said stream, means for continuously passing said stream of gas in contact with the filament of said first detector and then the filament of said second detector, recording means having one stylus for alternately recording the signals from either of said detectors, switch means normally connecting one of said detectors to said recording means, and automatic timer controlled switch-operating means for periodically disconnecting said one detector from said .recording means and connecting the other detector therewith.

4. In apparatus for detecting gas changes in formations encountered during drilling of a well bore by a bit while a fluid is circulated into and out of the well bore, including means for treating a series of possible gas containing specimens returned from apparently successive increments of depth of said well bore to cause gas to evolve therefrom, and means for testing the gas evolving during treatment of each said specimen for hydrocarbon gases, including a catalytic filament contacted by said gas and an electrical circuit for supplying current to said filament and means for indicating an effect produced at said filament by such catalytic combustion, the improvement comprising separate catalytic filaments; means for causing gas evolving during treatment of each said specimen to contact said filaments; and a separate similar electrical circuit for each catalytic filament, each said circuit including a source of electricity for supplying an electric current to said catalytic filament, means for adjusting the voltage of such current so as to apply a different voltage to said catalytic filaments independently and simultaneously, and

means for indicating an efiect produced at each said filament by such catalytic combustion, so as to obtain an indication of the difference in ratio between the effect produced at said filaments by such difierent voltages for a series of such specimens returned from successive increments of depth of said well bore.

5. A method of detecting gas changes informations encountered during drilling of a Well bore by a bit while a fluid is circulated into and out of the well bore, which comprises subjecting a series of possible gas containing specimens returned from apparently successive increments of depth of said well bore to treatment to evolve gas contained therein; contacting at least a portion of the gas evolved from each said specimen with two separate catalytic .filaments and in the presence of a combustion supporting gas; passing an electric current through said filaments independently and at different voltages, one said voltage being higher than the other and having a value tending to cause catalytic combustion of combustible gas components, including methane, which contact said filament, and the other said voltage being lower and having a value tending to cause catalytic combustion of combustible gas components, except'methane; which contact said other filament; and independently measuring, for each said specimen, an efiect produced at each said separate filament by catalytic combustion and thereby'determine for said successive increments of depth'diflerences in the ratio between the measurements for said higher and lower voltage values.

References Cited in the file of this patent UNITED STATES PATENTS 

5. A METHOD OF DETECTING GAS CHANGES IN FORMATIONS ENCOUNTERED DURING DRILLIING A WELL BORE BY A BIT WHILE A FLUID IS CIRCULATED INTO AND OUT OF THE WELL BORE, WHICH COMPRISES SUBJECTING A SERIES OF POSSIBLE GAS CONTAINING SPECIMENS RETURNED FROM APPARENTLY SUCCESSIVE INCREMENTS OF DEPTH OF SAID WELL BORE TO TREATMENT TE EVOLVE GAS CONTAINED THEREIN; CONTACTING AT LEAST A PORTION OF THE GAS EVOLVED FROM EACH SAID SPECIMENT WITH TWO SEPARATE CATALYTIC FILAMENTS AND IN THE PRESENCE OF A COMBUSTION SUPPORTING GAS; PASSING AN ELECTRIC CURRENT THROUGH SAID FILAMENTS INDEPENDENTLY AND AT DIFFERENT VOLTAGES, ONE SAID VOLTAGE BEING HIGHER THAN THE OTHER AND HAVING A VALUE TENDING TO CAUSE CATALYTIC COMBUSTION OF COMBUSTIBLE GAS COMPONENTS, INCLUDING METHANE, WHICH CONTACT SAID FILAMENT, AND THE OTHER SAID VOLTAGE BEING LOWER AND HAVING A VALUE TENDING TO CAUSE CATALYTIC COMBUSTION OF COMBUSTIBLE GAS COMPONENTS, EXCEPT METHANE, WHICH CONTACT SAID OTHER FILAMENT; AND INDEPENDENTLY MEASURING, FOR EACH SAID SPECIMEN, AND EFFECT PRODUCED AT EACH SAID SEPARATE FILAMENT BY CATALYTIC COMBUSTION AND THEREBY DETERMINE FOR SAID SUCCESSIVE INCREMENTS OF DEPTH DIFFERENCES IN THE RATIO BETWEEN THE MEASUREMENTS FOR SAID HIGHER AND LOWER VOLTAGE VALUES. 